What is the next step in managing a patient with dizziness and ataxia with a normal Magnetic Resonance Imaging (MRI) scan?

Management of Dizziness and Ataxia with Normal MRI

The next step is to determine the specific type of ataxia through targeted clinical examination and then pursue cervical/thoracic spine MRI for sensory ataxia or consider metabolic/genetic workup for cerebellar ataxia, rather than repeating brain imaging. 1

Clinical Differentiation of Ataxia Type

The critical first step is distinguishing between cerebellar ataxia and sensory/proprioceptive ataxia through physical examination, as this fundamentally changes your diagnostic pathway 1:

Cerebellar Ataxia Features

• Incoordination that does not worsen with eyes closed 2
• Wide-based gait, dysmetria, intention tremor, dysarthria 1
• Next step: MRI head without IV contrast (if not already done with adequate cerebellar protocol) or MRI head without and with IV contrast to assess for cerebellar atrophy, degenerative changes, or subtle pathology not visible on initial imaging 1

Sensory Ataxia Features

• Loss of proprioception out of proportion to other sensory modalities and motor function 1
• Symptoms markedly worsen with eyes closed (Romberg positive) 2
• Next step: MRI cervical and thoracic spine without IV contrast to evaluate dorsal columns for compressive myelopathy, B12/copper deficiency changes, or tabes dorsalis 1
• Add contrast if inflammatory, infectious, or neoplastic causes are suspected 1

Metabolic and Laboratory Evaluation

For sensory ataxia with normal spine imaging, pursue targeted metabolic workup 1:

• Vitamin B12 and copper levels (dorsal column degeneration) 1
• Syphilis serology if risk factors present (tabes dorsalis) 3
• Thyroid function, vitamin E levels for treatable causes 4

For cerebellar ataxia with normal or non-diagnostic brain MRI 4:

• Genetic testing for hereditary spinocerebellar ataxias (SCA) if family history or young age 1
• Paraneoplastic antibody panel if subacute onset 4
• Celiac serology (gluten ataxia) 4
• Alcohol history and thiamine levels 4

Vascular Evaluation if Chronic Recurrent Pattern

If the dizziness component is chronic recurrent with brainstem neurologic deficits suggesting vertebrobasilar insufficiency 1:

• MRA or CTA of head and neck to evaluate posterior circulation vasculature 1
• Consider transcranial Doppler ultrasound for dynamic vascular flow assessment 1
• Conventional diagnostic angiography may be needed for positional insufficiency evaluation in select cases 1

Advanced Imaging Considerations

Brain PET imaging may detect presymptomatic neuronal dysfunction in certain spinocerebellar ataxias before MRI changes appear, particularly if genetic testing suggests SCA 1

Critical Pitfalls to Avoid

• Do not repeat brain MRI without specific indication—the yield is extremely low if initial imaging was adequate 1
• Do not miss spinal cord pathology in sensory ataxia—this is the highest-yield next test 1
• Do not overlook treatable causes: B12/copper deficiency, hypothyroidism, celiac disease, neurosyphilis 1, 3, 4
• Do not order CTA/MRA for isolated cerebellar ataxia without vascular symptoms—focus on metabolic and genetic causes instead 1

When Dizziness Predominates Over Ataxia

If the presentation is primarily chronic disequilibrium rather than true ataxia 1:

• Consider autonomic dysfunction testing, even without orthostatic symptoms 1
• Evaluate for vestibular causes: perform bedside vestibular testing including Dix-Hallpike and HINTS examination 5, 3, 6
• MRI head and internal auditory canal with contrast if unilateral hearing loss or tinnitus suggests Meniere disease or vestibular schwannoma 1, 5